Current techniques for fabrication of precision, close tolerance, metal components typically require multiple process steps to produce a finished part. Often this involves preliminary steps (e.g. stamping, casting, forging, etc.) to create a semi-formed blank followed by precision machining, electric discharge machining (EDM), grinding and/or polishing to complete the part. This multiple step process is costly in terms of material handling, special tooling and fixturing, and material wastage associated with finishing the part.
The fabrication of precision millimeter wave (MMW) length radio frequency components and sabots for small caliber armor piercing ammunition present particularly difficult problems. As a general rule size and tolerance requirements for RF components scale with wavelength. Allowable dimensional tolerances are reduced to approximately .+-.25 microns (0.001 inch) for frequencies above 40 GHz and .+-.13 microns (0.0005) for frequencies above 75 GHz. Development of increasingly compact, higher frequency microwave and sub-millimeter systems for smart munition guidance, automobile collision avoidance, and communication applications have created significant fabrication challenges, particularly in terms of achieving economical high volume production.
Sabots for small caliber armor piercing ammunition such as the 25 MM round are currently machined from 7075-T6 aluminum. Each sabot is comprised of three separate 120-degree segments. The dimensional tolerance for each pressure flank is .+-.0.0005 inches. The three 120-degree segments are milled to precise tolerances and are individually numbered and mated together. Secondary machining operations are necessary to manufacture a complete sabot from the mated segments. The positioning of each segment is not interchangeable and the required CNC machining is time consuming and costly.
Fabrication of MMW and sub-millimeter wavelength components and housings and sabots for small caliber armor piercing ammunition rely heavily on CNC machining, EDM and/or electro-forming techniques. While these techniques can provide technically adequate MMW components and sabots, they do so only at unacceptably high piece part costs. In addition these techniques are poorly suited for high volume applications. Furthermore, as new applications are developed for sub-millimeter technologies, these techniques will be less and less capable of satisfying all of the technical requirements.
Therefore there is a critical need for fabrication processes that are capable of producing components to the precision required for MMW and sub-millimeter applications and sabots for small caliber armor piercing ammunition. The new fabrication processes must be competitive with current techniques and be capable of scaling to high volume production while preserving their cost advantage.